This invention is in answer to the steady increase of the use of hotter burning gun powder for performance and the full automatic utilization for more rounds per minute. Both characteristics have continued to push the gun barrel life to the limit with regard to hot strength and barrel erosion. Until now, many attempts have been made to improve barrel performance with insufficient success. It is safe to say that gun barrel performance has been one of the primary limits to the increase of gun firepower.
A new method for increasing gun barrel performance is disclosed herein and is more than simply a gun barrel coating or lubricant. The present invention is a simple but effective method for enhancing the performance of the gun barrel itself and introduces additional benefits noted herein.
One object of the present invention is to provide a simple but meaningful method of combining the metal of the gun barrel with a fine particulate ceramic, and combining the advantages of both in a synergistic combination.
Another object of the present invention is to allow a bullet to be primarily guided down a gun barrel by embedded ceramic particulate in the surface of the gun barrel resulting in a reduction in friction and heat compared to a typical gun barrel.
Another object of the present invention is to reduce gun barrel wear by the use of renewable ceramic surfaces.
Another object of the present invention is to reduce or eliminate barrel cleaning. This is especially noteworthy in full automatic firing and black powder applications.
Another object of the present invention is to improve accuracy due to the higher velocity provided by reduced friction and improved bullet to barrel sealing.
Another object of the present invention is to prevent rust corrosion in the barrel bore without the necessity of oiling or other treatment. Another object of the present invention including all of the above is the application of the invention to black powder guns and shotgun wadding or packing.
There are several advantages to the present invention. One result is prolonged gun barrel life allowing for hotter powder loads and higher rates of fire. This is achieved by an original surface interface between bullet and gun barrel being filled by a ceramic dry lubricant which remains in place or is periodically replaced. Another advantage is reduced or eliminated gun barrel cleaning. This results due to excess ceramic particulate being discharged through a barrel muzzle, leaving behind a clean barrel. Another advantage is increased muzzle velocity. This is achieved by the ceramic dry lubricant providing reduced friction and improved bullet seal, reducing vibration or “chatter” of a bullet traveling down the gun barrel. Another advantage is the elimination of gun barrel corrosion. Corrosion or rust can only begin in metal grain boundaries, which, according to the present invention, are filled with the sub-micron sized particles of the ceramic dry lubricant. Another advantage is increased accuracy. This results because the bullet time-to-target is reduced as a result of increased muzzle velocity. Accuracy is increased also due to the reduced stress caused by reduction of friction and heat. Accuracy is also increased as a result of a more consistent bullet seal achieved by the present invention. A final advantage is the inexpensive nature of the present invention, which can be practiced in the field on existing gun barrels.
The present invention uses the materials described herein in the manner in which they are best utilized. The metal surface of the internal bore of a gun barrel is used as a shape and form matrix, and the dry ceramic is used as a lubricant and wear surface. The typical steel barrel has become a standard due to its high heat and strength, its ability to air cool and be mass produced, and its ductility.
The original conception behind the present invention was to provide a practical way to maintain the integrity of a gun barrel in order to maintain accuracy and reduce the maintenance without a great increase in cost. Dry ceramic lubricant, such as boron nitride powder having sub micron-sized particulate applied in a dispersion mode, prevents burning the metal surface of a gun barrel. This offers the best available method of protecting metal surfaces from oxidation works as may be normally anticipated.
The dry ceramic such as boron nitride powder, in sub-micron size, can be manually rolled or burnished into the grain boundaries of a steel barrel or it can burnished by coating a bullet or other ammunition equipment prior to firing the gun, allowing the bullet to do the burnishing when it is fired. This simplistic method of bullet burnishing was selected because it does not require any special tooling and can allow for field processing. Firing boron nitride powder coated bullets utilizes the velocity, heat, and pressure resulting from the firing to do the work of lodging the ceramic particles into the grain boundaries of the composite steel.
In order to take advantage of the benefits of the present invention by coating bullets with boron nitride powder to fire through the barrel and coat the internal bore, the gun barrel must first be very clean so that the ceramic particulate can be driven into the grain boundaries of the steel composite. This also requires that no lubricant or rust preventative be present. The ceramic also fills unused voids in a gun barrel, such as scratches or wear, thereby affecting an improved seal. Unused particulate passes out of the gun barrel upon firing. Minor excess of boron nitride powder assures that the barrel is clean and ready for the next round. Because the interior surface is then basically the ceramic powder, there is no detriment noted in this process.
The dry ceramic lubricant selectively used in the process comprises boron nitride powder (HBN) having a hexagonal (laminar) microstructure. Such boron nitride powder is considered a dry lubricant because it develops an internal sheer plane in its body, which reduces friction. There are other boron nitride powder types which are relatively hard (e.g. CBN, PBN) which are inappropriate for use in the disclosed method and apparatus herein.
The present invention generally comprises a dry lubricant ceramic that separates the ammunition projectile from the internal bore of a metal gun barrel. This provides a dynamic friction reduction, a dynamic pressure seal, a replaceable wear surface, and a very effective gun bore cleaning action. The present invention has been tested with extremely positive results on shotgun wads (modern plastic material) and black powder muzzle loaders, using boron nitride powder coated patches and sabots.
Secondary Ion Mass Spectrometry (SIMS) testing performed on the surfaces of the internal bore of gun barrels shows that the boron nitride powder used in accordance with the present invention results in the ceramic powder particulates being clearly embedded within the grain boundaries of the metal gun barrel. These test results show that burnishing sub-micron particulate ceramic is effective, and that continued firing of uncoated bullets will continue to experience the advantages of the present invention for an extended period of time. Such testing also shows that excessively coating boron nitride powder onto bullets provides erratic results and sometimes no velocity improvement. Thinner coating on the bullets provides more consistent velocity improvement.
Most of the prior art in this area does not indicate a complete understanding of the application of ceramics in the present invention. Although ceramics, as metal oxides, have many advantages, they also have many disadvantages such as poor tensile strength, poor thermal shock resistance, and difficult and expensive processing. Boron nitride powder in accordance with the present invention, however, provides many distinct advantages while avoiding several of these disadvantages and maintaining basic simplicity and relatively minor cost.
The use of boron nitride powder coatings in black powder guns is also significantly advantageous. Black powder gun shooting generally provides difficult clean up after only a few rounds are fired. Such clean up is nasty and time consuming. Preliminary testing of black powder guns using boron nitride powder coated patches and sabots shows positive results. Results in black powder guns include greater accuracy as well as avoiding the need to clean the bores.
The hexagonal (laminar) structure of boron nitride powder allows it to sheer apart in laminations or layers in the direction of the least friction, similar to what happens using molybdenum disulfide (MO), a well-known dry lubricant. Nevertheless, boron nitride powder has better self-sustaining qualities than MO, which is a refractory metal oxide.
Because of very close grain boundaries in stainless steel gun barrels, the present invention is not as effective as in composite steel gun barrels. Chemical etching or mechanical resurfacing may be required. Furthermore, commercial chrome plating in gun barrels will not permit grain boundary use in accordance with the present invention. As a result, the present invention provides a good replacement for the far more costly chrome plating process and is effective when the heat generated from use of a gun barrel has stripped off the chrome plating in the barrel due to the heat, which inevitably occurs anyway.